The present invention relates to a refrigerator having liquid heat exchangers and an air heat exchanger.
Among refrigerator which simultaneously feed hot water and cold water has been a refrigerator which includes a compressor for compressing refrigerant, a hot water heat exchanger, an expander, a cold water heat exchanger, an air heat exchanger, a discharge three-way valve provided on discharge side of the compressor, and a suction three-way valve provided on suction side of the compressor (JP S56-7955 A).
In an operation primarily for cooling in which a thermal load on the cold water heat exchanger is larger than a thermal load on the hot water heat exchanger, the conventional refrigerator sets an opening of the discharge three-way valve so that discharge refrigerant is fed from the compressor to the hot water heat exchanger and the air heat exchanger at flow rates in a predetermined ratio and sets an opening of the suction three-way valve so that refrigerant is fed only from the cold water heat exchanger to the compressor. Thus the air heat exchanger functions as a condenser so that the thermal loads are balanced between the cold water heat exchanger with the comparatively large thermal load and the hot water heat exchanger with the comparatively small thermal load.
In an operation primarily for heating in which the thermal load on the hot water heat exchanger is larger than the thermal load on the cold water heat exchanger, on the other hand, the conventional refrigerator sets an opening of the discharge three-way valve so that discharge refrigerant from the compressor is fed only to the hot water heat exchanger and sets an opening of the suction three-way valve so that refrigerant is fed from the cold water heat exchanger and the air heat exchanger to the compressor at flow rates in a predetermined ratio. Thus the air heat exchanger functions as an evaporator so that the thermal loads are balanced between the hot water heat exchanger with the comparatively large thermal load and the cold water heat exchanger with the comparatively small thermal load.
The discharge three-way valve and the suction three-way valve are made of solenoid three-way valves, and openings of the valves are separately controlled by a controller. The controller detects the thermal loads on basis of an actual temperature of water that undergoes heat exchange in the cold water heat exchanger, an actual temperature of water that undergoes heat exchange in the hot water heat exchanger, and temperature differences between the actual temperatures and target temperatures, and the controller controls the openings of the discharge three-way valve and the suction three-way valve so as to balance the thermal loads.
When a condensing pressure of the refrigerant in the hot water heat exchanger is greatly larger than a condensing pressure of the refrigerant in the air heat exchanger in this type of refrigerator performing the operation primarily for cooling, so-called stagnation may occur in which the refrigerant stagnates in the air heat exchanger.
Therefore, it has conventionally been thought that the stagnation of the refrigerant can be prevented by control in which the controller sets the opening of the discharge three-way valve on the air heat exchanger side to be not smaller than 30% and not larger than 100%. That is, the control by which a minimum opening of the discharge three-way valve on the air heat exchanger side is set larger than the opening of 30% that prevents the stagnation of the refrigerant in the air heat exchanger is conceivable on an assumption that outside air where the air heat exchanger is positioned has a predetermined lowest temperature, that a target temperature of water from the hot water heat exchanger is set as a highest temperature, and that a largest pressure difference is thus caused between the condensing pressure in the hot water heat exchanger and the condensing pressure in the air heat exchanger.
The refrigerator, however, is supposed to control the opening of the discharge three-way valve on the hot water heat exchanger side within a range from 0% to 70% because the refrigerator controls the opening of the discharge three-way valve on the air heat exchanger side within a range from 30% to 100%. Therefore, a problem is caused in which it is difficult to accurately control temperature of water being heated by the hot water heat exchanger.